Responses

True... Actually, for me it depends on who the main character is.
But yes, I feel that same anxiety, too.
So if I get hurt by stories and stuff, I could only imagine the pain felt by real life couples. I'm sparing myself of that, thanks.
WARNING: CONTAINS SPOILER ლ(´ڡ`ლ)
I'm actually partial about this manga. I mean, when the situation is like this, where the guy has a girlfriend, and another girl starts to get close to him, I get irritated.
Imagine if you are his girlfriend. Because you're not by his side, he starts to get lonely. Then, another girl entertains him, and he starts thinking less of you and thinking more of her. Eventually, the only thing that links you to him is a promise he made that he'd make you happy/he'd be with you forever. But, would that really make you happy? I find it unfair. Because then, you'd only be fooling yourselves. However, if I were the 'other' girl, even if he chooses me over his girlfriend, I would have a little worry at the back of my mind. "What if it happens to me next time? If, even though I'm his girlfriend now, he meets someone else and he suddenly feel differently for her? Would he just keep dating me for the sake of it, or would he choose the new girl over me, just like how he chose me over his girlfriend before?"
Well, in this manga, we sympathize with Totoki because Haruka turns out to be emotionally/mentally unstable, thus, making her the "psycho girlfriend" of our gentle and handsome lead. Because her thoughts and actions were actually very selfish, we start cheering for the new girl who doesn't tie Yukimura down by a mere duty and let him experience a normal life instead.
I admire Yukimura's attempt of cutting his connection with Totoki because he's starting to fall for her, when he already has a girlfriend. However, even if he chose to stay with Haruka, it was obvious that things can't go back to the way they were before. His heart wasn't hers anymore. Or perhaps, she's been losing him bit by bit from when she started acting the way she did.
Anyway, I'm happy about how things ended up, but I would've loved more backstory for Haruka and Yukimura, and how things progressed for Yukimura and Totoki.
ps. I liked how they incorporated Sleeping Beauty in the story.